1. Field of the Invention
The present invention relates to a precision cutting apparatus for cutting workpieces such as semiconductor wafers or ferrite pieces, and more specifically a precision cutting apparatus using two blades for the purpose of improving the efficiency with which the cutting apparatus can cut workpieces.
2. Description of Related Art
Japanese Patent 3-11601(B) shows such a dual-blade type of precision cutting apparatus for use in dicing semiconductor wafers. It has two parallel-arranged spindle units rotatably supported in their spindle housing, each spindle unit having a cutting blade mounted to the tip end of the rotary axis. The direction in which these spindle units are arranged is referred to as xe2x80x9cYxe2x80x9d-axial direction.
In making step cutting of a semiconductor wafer such a dicing apparatus can be advantageously used; one of the two cutting blades is a xe2x80x9cVxe2x80x9d-edged blade for cutting a xe2x80x9cVxe2x80x9d-shaped groove, and the other is a sharp-edged (or xe2x80x9cIxe2x80x9d-edged) blade for cutting the bottom of the xe2x80x9cVxe2x80x9d-shaped groove forming a Y-shape in cross-section, thus separating the semiconductor wafer into a plurality of chips, each having a top chamfered in all sides.
Such parallel-arrangement of two spindle units in the cutting direction or xe2x80x9cXxe2x80x9d-axial direction (and hence the two cutting blades arranged side by side in the xe2x80x9cXxe2x80x9d-axial direction) requires the spindle units to move excessively for the inter-blade center distance beyond the semiconductor wafer after crossing the full length of the workpiece because otherwise, the following blade cannot cut the workpiece to its extremity on either side of the workpiece. Apparently the overrunning on either side of the workpiece (or extra amount of cutting stroke) will lower the cutting efficiency accordingly.
In view of the above one object of the present invention is to provide a dual-blade type of precision cutting apparatus which can cut workpieces at an increased efficiency.
To attain this object a precision cutting apparatus comprising a chuck table for holding a workpiece to be cut, and first and second cutting means for cutting the workpiece held by the chuck table, is improved according to the present invention in that: the first cutting means includes a first spindle unit to which a first blade is to be fixed; the second cutting means includes a second spindle unit to which a second blade is to be fixed; and the first and second cutting means are series-arranged in linear alignment with their first and second blades opposing to each other. The series-arrangement of the first and second cutting means permits the sweeping of the cutting blades across the full width of the workpiece, not requiring the overrunning beyond either side of the workpiece as is the case with the parallel-arrangement of two cutting blades, thus leading to a substantial improvement in cutting efficiency.
The above described arrangement can be reduced to practice as follows:
the first and second cutting means and the chuck table are adapted to move relative to each other in the X-axial direction across the Y-axial direction in which the axes of the first and second spindle units are aligned, thereby permitting the workpiece held by the chuck table to be cut in the X-axial direction;
the first and second cutting means and the chuck table are adapted to move relative to each other in the Z-axial direction across the X-axial and Y-axial directions, thereby permitting the cutting depth to be adjusted by determining the Z-axial position of the first and second cutting means relative to the Z-axial position of the chuck table; and
the first and second cutting means are adapted to move independently in the Y-axial direction, thereby permitting the first and second cutting means to move toward or apart from each other by moving the first cutting means and/or the second cutting means in the Y-axial direction.
Also, a precision cutting apparatus comprising a chuck table for holding a workpiece to be cut, the chuck table being adapted to travel on-cutting path formed in the X-axial direction, and first and second cutting means for cutting the workpiece is improved according to the present invention in that: the first cutting means includes a first spindle unit to which a first blade is to be fixed; the second cutting means includes a second spindle unit to which a second blade is to be fixed; and the first and second cutting means hang from an indexing-and-feeding path extending in the Y-axial direction and straddling the feeding-and-cutting path, the first and second blades of the first and second cutting means being in opposing relation, and being permitted to be incrementally fed independently in the Y-axial direction.
The cutter-suspending arrangement permits the compact designing of the cutting apparatus, facilitating the feeding-and-cutting of workpieces.
The above described arrangement can be reduced to practice as follows:
an upright guide wall has the indexing-and-feeding path provided on one side of the guide wall, the upright guide wall having a gate-like opening, not interfering with the feeding of the chuck table for cutting operation;
a guide rail or rails are laid on the indexing-and-feeding path for guiding the indexing-and-feeding of the first and second cutting means in the Y-axial direction;
a linear scale is along the indexing-and-feeding path, thereby permitting the indexing-and-feeding of the first and second cutting means in the Y-axial direction to be controlled with the aid of the linear scale;
a single linear scale is provided to be used by the first and second cutting means in common;
the first and second cutting means are adapted to be driven by associated threaded rods;
the first and second cutting means have threaded rods exclusively allotted thereto for independent drive; and
the first and second cutting means have a threaded rod in common, each cutting means having a feeding nut threadedly engaged with the threaded rod.
A cutting method according to the present invention uses a precision cutting apparatus comprising a chuck table for holding the workpiece, and first and second cutting means for cutting the workpiece held by the chuck table, the first cutting means including a first spindle unit to which a first blade is to be fixed, and the second cutting means including a second spindle unit to which a second blade is to be fixed, the first and second cutting means being series-arranged in linear alignment with their first and second blades opposing to each other, the first and second cutting means and the chuck table being adapted to move relative to each other in the X-axial direction across the Y-axial direction in which the axes of the first and second spindle units are aligned, thereby permitting the workpiece held by the chuck table to be cut in the X-axial direction. The cutting method using such a precision cutting apparatus comprises the steps of: putting the first and second blades on the opposite sides of the workpiece in the Y-axial direction; moving the first and second blades toward each other step by step, thereby allowing each blade to advance an incremental distance toward the center of the workpiece; and making the first and second cutting means and the chuck table to move relative to each other in the X-axial direction, thereby cutting the workpiece.
One of the first and second cutting blades is selectively used in cutting the uncut area of workpiece which remains between the first and second blades when getting closest to each other in case that the minimum inter-distance remaining therebetween is longer than the incremental feeding distance. The first and second cutting blades are of same kind.
The cutting method according to another aspect of the present invention comprises the steps of: putting the first and second blades at the center of the workpiece; moving the first and second blades apart from each other step by step in the Y-axial direction, thereby allowing each blade to withdraw an incremental distance toward one or the other side of the workpiece; and making the first and second cutting means and the chuck table to move relative to each other in the X-axial direction, thereby cutting the workpiece.
One of the first and second cutting blades is selectively used in cutting the uncut area of workpiece which remains between the first and second blades when putting them at the center of the workpiece in case that the minimum inter-distance remaining therebetween is longer than the incremental feeding distance. The first and second cutting blades are of same kind.
The cutting method as described above requires no extra amount of cutting stroke beyond the periphery of the workpiece.
The cutting method according to still another aspect of the present invention comprises the steps of: putting the first blade on one side of the workpiece and the second blade at the center of the workpiece; moving the first blade toward the center of the workpiece and the second blade toward the other side of the workpiece in the Y-direction, thereby allowing the first and second cutting means to move an incremental distance in one and same direction; and making the first and second cutting means and the chuck table to move relative to each other in the X-axial direction, thereby cutting the workpiece. The first and second cutting blades are of same kind.
When a rectangular or square workpiece is diced, this cutting method cannot be allowed to run vainly at any times while cutting all streets of the workpiece two by two simultaneously.
The cutting method according to still another aspect of the present invention comprises the steps of: putting the first blade in a first cutting position on the workpiece; making the first cutting means and the chuck table to move relative to each other in the X-axial direction, thereby forming a groove in the workpiece; putting the second blade in the groove thus formed in the workpiece; and making the second cutting means and the chuck table to move relative to each other in the X-axial direction, thereby cutting the remaining bottom of the groove. The first and second cutting blades are of different kinds.
According to this cutting method it requires no extra amount of cutting stroke beyond the periphery of the workpiece and also enables to perform step cutting with different kinds of cutting blades in combination.
Other objects and advantages of the present invention will be understood from the following description of preferred embodiments of the present invention, which are shown in accompanying drawings.